Same problem with ASUS USB-N10 adapter. Was working perfect with Backtrack 5 R1, upgrade to R2-R3 messed it up.
It uses the r8712u module (RTL8712U).
I tried recompiling it with the 3.1.9 kernel source (as mentioned above) with no luck. (Kernel source downloaded from www.kernel.org)
It compiles fine and everything seems normal until I try to load the module, then I get a bunch of "Call trace:"-errors in syslog.
I guess Backtrack got some modifications thats not compatible.
Anyone found any solution or new working drivers?